1. Field of the Invention
This invention relates to zoom lenses for television cameras and, more particularly, to zoom lenses capable of macro photography and tracking adjustment.
2. Description of the Related Art
As the lens for television is releasably attached to the camera body, the sharp image plane of the lens has, despite interchanging of it, to be brought into coincidence with the image receiving surface of the pickup device in the camera body. For this purpose, it has already been known to provide a technique that moves the relay lens group of the zoom lens, or the so-called "tracking" adjustment.
It is also known to provide a technique of making macro photography by moving the relay lens group.
By the way, to make it possible to use the same relay lens in both macro photography and tracking adjustment, Japanese Patent Publication No. Sho 58-1401 proposes a technique that after it has once been moved to make macro photography, the relay lens group returns to the original tracking adjusted position again in automatic response to transition to the normal photography mode.
In the above-described Japanese Patent Publication No. Sho 58-1401, however, for only one lens group, in this instance, the relay lens is made to perform the dual function, there is need to employ the operating mechanism for macro photography, the tracking control mechanism, and further a mechanism for coordinating these two mechanisms with each other.
The use of such a technique, therefore, not only involves great increases of the complexity of mechanical structure and the size of the casing therefor, but also requires a high precision accuracy in each of the mechanisms and another mechanism for returning the lens group for tracking to the adjusted position.